Method for forming Ta2O5 dielectric layer using plasma enhanced atomic layer deposition

ABSTRACT

A method for forming a Ta 2 O 5  dielectric layer using plasma enhanced atomic layer deposition, which can improve the quality of a layer and its electric property by forming a Ta 2 O 5  dielectric layer using a plasma enhanced atomic layer deposition. The method for forming a Ta 2 O 5  dielectric layer using plasma enhanced atomic layer deposition, comprising the steps of: a) flowing Ta(OC 2 H 5 ) 5  source gas in a chamber and generating plasma; b) depositing a Ta 2 O 5  layer by using the plasma; c) purging the chamber; d) repeatedly performing the steps a) to c) in order to form a Ta 2 O 5  dielectric layer; e) thermally treating the surface of the Ta 2 O 5  dielectric layer in an oxygen atmosphere; and f) crystallizing the Ta 2 O 5  dielectric layer.

BACKGROUND

1. Technical Field

A method for forming a dielectric layer of a capacitor in asemiconductor device is disclosed. More particularly, a method forforming a Ta₂O₅ dielectric layer using a plasma enhanced atomic layerdeposition is disclosed.

2. Description of the Related Art

As the level of integration increases in semiconductor devices likeDRAMs (Dynamic Random Access Memory), superior electrical properties,such as high charge capacity in a limited space and reduced leakagecurrent are needed in a DRAM capacitor. For this reason, a Ta₂O₅dielectric layer, which is a high dielectric layer, is used for thedielectric layer of the capacitor.

Meanwhile, in case of a Ta₂O₅ dielectric layer deposited by the LPCVD(Low Pressure Chemical Vapor Deposition) method, the electric propertyof a capacitor deteriorates because of inferior step coverage.

To solve this problem, the atomic layer deposition (ALD) is used toimprove the step coverage by repeatedly depositing a plurality of atomiclayers.

FIGS. 1A to 1D are cross-sectional views illustrating the conventionalmethod for forming a Ta₂O₅ dielectric layer.

First, as shown in FIG. 1A, after a polysilicon layer 11 to form abottom electrode is deposited on a substrate 10 on which transistors andplugs are formed, the native oxide layer (now shown) on the surface ofthe polysilicon layer 11 is removed with HF or BOE (Buffer OxideEtchant), and then the surface of the polysilicon layer 11 is subject tothe RTP (Rapid Thermal Process) in the atmosphere of NH₃.

Subsequently, as illustrated in FIG. 1B, a Ta₂O₅ dielectric layer 12A isdeposited on the layer 11 by performing the atomic layer deposition(ALD) and the in-situ treatment of oxygen (O₂) plasma.

Repeating these two procedures results in the depositing of a pluralityof Ta₂O₅ dielectric mono layers (12 ₁˜12 n) which produces a Ta₂O₅dielectric layer 12A with superior step coverage.

As illustrated in FIG. 1C, the process of oxygen (O₂) plasma treatmentis for thermally treating the Ta₂O₅ dielectric layer 12A in the oxygenatmosphere. This way, a crystallized Ta₂O₅ dielectric layer 12 isformed.

Then, as depicted in FIG. 1D, a capacitor in a stacked structure of apolysilicon layer 11, Ta₂O₅ dielectric layer 12 and top electrode 13 isformed by depositing a top electrode 13 on the Ta₂O₅ dielectric layer12.

The conventional method for forming a Ta₂O₅ dielectric layer using theatomic layer deposition (ALD) and oxygen plasma described above hasfollowing problems.

First, the poor reactivity of oxygen makes carbon A remain in the Ta₂O₅dielectric layer 12. Secondly, the weak activation energy of the oxygenstill makes oxygen vacancy in the Ta₂O₅ dielectric layer 12, causing itselectric property deteriorated by leakage current.

SUMMARY OF THE DISCLOSURE

A method for forming a Ta₂O₅ dielectric layer using a plasma enhancedatomic layer deposition that can improve the quality of a layer and itselectrical properties is disclosed.

More specifically, a method for forming a Ta₂O₅ dielectric layer usingplasma enhanced atomic layer deposition is disclosed that comprises: a)flowing Ta(OC₂H₅)₅ source gas in a chamber and generating plasma; b)depositing a Ta₂O₅ layer by using the plasma; c) purging the chamber;d)repeatedly performing the steps a) to c) in order to form a Ta₂O₅dielectric layer; e) thermally treating the surface of the Ta₂O₅dielectric layer in an oxygen atmosphere; and f) crystallizing the Ta₂O₅dielectric layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the disclosed process willbecome apparent from the following description of the preferredembodiments given in conjunction whit the accompanying drawings,wherein:

FIGS. 1A to 1D are cross-sectional views illustrating a conventionalmethod for forming Ta₂O₅ dielectric layer; and

FIGS. 2A to 2E are cross-sectional views depicting a method for forminga Ta₂O₅ dielectric layer in accordance with an embodiment of thisdisclosure.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The disclosed processes will now be described in conjunction with theaccompanying drawings, FIGS. 2A to 2E.

FIGS. 2A to 2E are cross-sectional views depicting a method for formingTa₂O₅ dielectric layer in accordance with the disclosed process.

First, as illustrated in FIG. 2A, after a polysilicon layer 21 to formthe bottom electrode is deposited on a substrate 20 formed with thesubstructure including transistors and plugs, the natural oxidationlayer (now shown) on the surface of the polysilicon layer 21 is etchedback with HF or BOE (Buffer Oxide Etchant), and then the surface of thepolysilicon layer 21 is treated with the RTP (Rapid Thermal Process) inan ambient atmosphere of NH₃.

Then, as illustrated in FIG. 2B, a Ta₂O₅ dielectric layer 22A is formedby flowing Ta(OC₂H₅)₅ source in the chamber and generating Ta and oxygenplasma.

The method for depositing a Ta₂O₅ dielectric layer 22A using the plasmaenhanced atomic layer deposition (PEALD) will be described more indetail.

Under the condition of substrate temperature ranging from about 200 toabout 300° C., a chamber pressure ranging from about 0.2 to about 10Torr with a RF power supply ranging from about 30 to about 500 W, aTa(OC₂H₅)₅ source gas at a temperature ranging from about 170 to about190° C. is flowed in the chamber at a speed ranging from about 0.006 toabout 0.1 cc/min for a time period ranging from about 0.1 to about 5seconds, thereby generating Ta and oxygen plasma.

Subsequently, with the same temperature and pressure conditionmaintained, a Ta₂O₅ mono layer 22 ₁ is deposited by depositing theplasma source gas on top of the substrate for a time period ranging fromabout 0.1 to about 0.5 seconds. Then, it is purged with a nitrogen orargon gas for a time period ranging from about 0.2 to about 5 seconds.

Repeating the three steps of Ta₂O₅ mono layer formation period severaltimes, a plurality of Ta₂O₅ mono layers are deposited and thus a Ta₂O₅dielectric layer 22A with superior step coverage is generated.

As shown in FIG. 2C, a surface-treated Ta₂O₅ dielectric layer 22B isformed by making oxygen or N₂O a plasma and treating the surface of theTa₂O₅ dielectric layer 22A with the plasma. Here, the carbon remainingin the surface-treated Ta₂O₅ dielectric layer 22B reacts tithe highlyreactive N₂O plasma to become CO or CO₂ and is purged. In addition, theoxygen vacancy inside the surface-treated Ta₂O₅ dielectric layer 22B issuppressed by the N₂O plasma with high activation energy.

Subsequently, as illustrated in FIG. 2D, annealing the surface-treatedTa₂O₅ dielectric layer 22B in an ambient of N₂O or oxygen at atemperature ranging from about 650 to about 800° C. for a time periodranging from about 10 to about 20 minutes, a crystallized Ta₂O₅dielectric layer 22 is formed.

Then, as illustrated in FIG. 2E, forming a top electrode on top of thecrystallized Ta₂O₅ dielectric layer 22, a capacitor in a stackedstructure of a polysilicon layer 21, crystallized Ta₂O₅ dielectric layer22 and top electrode 23 is completed.

As described above, the disclosed methods for forming a capacitorimprove step coverage by forming a Ta₂O₅ dielectric layer using plasmaenhanced atomic layer deposition, and electric property by making thelayer quality of the Ta₂O₅ dielectric layer better.

In short, the disclosed methods can improve the layer quality of theTa₂O₅ dielectric layer and heighten step coverage in a method forforming a Ta₂O₅ dielectric layer using plasma enhanced atomic layerdeposition.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

What is claimed:
 1. A method for forming a Ta₂O₅ dielectric layer usingplasma enhanced atomic layer deposition, comprising: a) flowingTa(OC₂H₅)₅ source gas in a chamber and generating a plasma; b)depositing a Ta₂O₅ layer with the plasma; c) purging the chamber; d)repeatedly performing the steps a) to c) in order to form a Ta₂O₅dielectric layer; e) thermally treating the surface of the Ta₂O₅dielectric layer in an oxygen atmosphere; and f) crystallizing the Ta₂O₅dielectric layer.
 2. The method as recited in claim 1, wherein step a)is carried out with a temperature of the substrate ranging from about200 to about 300° C.
 3. The method as recited in claim 2, wherein stepa) is carried out under a chamber pressure ranging from about 0.2 tabout 10 Torr.
 4. The method as recited in claim 3, wherein step a) iscarried out with a supplied RF electric power ranging from about 30 toabout 500 W.
 5. The method as recited in claim 1, wherein a temperatureof the Ta(OC₂H₅)₅ source gas ranges from about 170 to about 1900° C. 6.The method as recited in claim 5, wherein the Ta(OC₂H₅) ₅ source gas hasa flow rate ranging from about 0.006 to about 0.1 cc/min.
 7. The methodas recited in claim 6, wherein the Ta(OC₂H₅)₅ source gas is flowed for atime period ranging from about 0.1 to about 5 seconds.
 8. The method asrecited in claim 1, wherein step b) is carried out with a temperature ofthe substrate ranging from about 200 to about 300° C., and a chamberpressure ranging from about 0.2 to about 10 Torr.
 9. The method asrecited in claim 8, wherein step b) is carried out for a time periodranging from about 0.1 to about 0.5 seconds.
 10. The method as recitedin claim 1, wherein the chamber is purged with nitrogen or argon. 11.The method as recited in claim 1, wherein the chamber is purged for atime period ranging from about 0.2 to about 5 seconds.
 12. The method asrecited in claim 1, wherein during step e), the surface of the Ta₂O₅dielectric layer is treated with an oxygen plasma or a N₂O plasma. 13.The method as recited in claim 1, wherein step f) is carried out in anoxygen or N₂O atmosphere.
 14. The method as recited in claim 13, whereinstep f) is carried out at a temperature ranging from about 650 to about800° C.
 15. The method as recited in claim 14, wherein the step f) iscarried out a time period ranging from about 10 to about 30 minutes.